"It's about 3,000 degrees inside there, and then when we put 250 pounds of iron in there, it melts and it falls down into a well, and then we tap that out every 20 minutes and into ladles," Potratz said.

"Then we start pouring until we see it coming up the vent cups, and once it fills up to the top, then we're good -- we move on to the next mold," said Jim Williams, who took part in the event.